Ridge-induced tectonic heterogeneity: Reappraising the Devonian geodynamic mechanism along the southeastern Central Asian Orogenic Belt

Continental crustal growth mechanisms remain a pivotal frontier in geoscience. The Central Asian Orogenic Belt (CAOB), Earth’s largest accretionary orogen, provides critical insights into Phanerozoic crustal evolution. Devonian records along the southeastern CAOB are key to deciphering mid-Paleozoic crustal growth. This study presents an integrated analysis of newly discovered Devonian magmatic suites from the northern Liaoning and middle Jilin regions of Northeast China. Zircon U-Pb dating shows that these rocks formed between the late Early and latest Devonian (ca. 410–360 Ma). They display variable initial 87Sr/86Sr ratios, positive εNd(t) and εHf(t) values, and young model ages, indicating a mix of depleted mantle-derived magma and basic lower crust lacking ancient basement. To clarify the tectonic geodynamics and lateral connections, we integrated a review of Devonian magmatism along the southeastern CAOB, revealing an ~1300-km-long magmatic belt. The Sr-Nd-Hf isotopic data demonstrate that the Devonian magmatic rocks in the middle western part mainly originated from variably enriched mantle components with different involvement of ancient lower-crustal material controlled by vertical crustal growth, whereas the rocks in the eastern part were generally derived from partial melting of the lower crust or depleted-mantle sources controlled by lateral crustal growth. Integrating geochemical data with machine learning–driven crustal thickness analysis, we infer that the southeastern CAOB evolved from an Andean-type continental margin influenced by a ridge-induced slab window in the west to a western Pacific–type margin in the east. This spatial transition records the Middle Devonian onset of heterogeneous southward subduction of the Paleo-Asian Ocean.